1. Technical Field
This description generally relates to the field of wireless communication devices, and more particularly to encoding wireless communication devices.
2. Description of the Related Art
Wireless communication devices, including wireless memory devices for storing and retrieving data, such as radio frequency identification (“RFID”) tags, are used in a variety of environments. Such devices typically employ an antenna structure coupled to a wireless transponder circuit to transmit and/or receive data via electromagnetic signals in some frequency range.
Antenna structures may include a primary antenna element driven by a transmitter to transmit data in an outgoing signal and/or driven by an external signal from an external source to receive incoming data. Antenna structures may further include parasitic antenna elements that electromagnetically cooperate with the primary antenna element to enhance the transmission or reception of a signal.
The wireless transponder circuit found in many wireless memory devices typically includes a memory portion and a logic portion. The memory portion stores data, while the logic portion controls the reading, writing, and manipulation of data in the memory portion. The logic portion may further couple between the memory portion and the antenna to act as a transmitter, receiver, or transceiver for reading and/or writing data to and/or from the wireless memory device.
Active wireless communication devices include a discrete consumable power source, such as a battery, to provide power to the wireless transponder circuit. In contrast, passive wireless communication devices derive power from a wireless interrogation signal, for example, by backscattering the signal as a response signal encoded with information from the wireless memory device.
Wireless communication devices may be provided in an array spaced at predetermined increments along media or another substrate. Before deployment, a wireless encoder (often referred to as a “printer”) may be used to send an electromagnetic signal conveying information to each wireless communication device as the media carrying the wireless communication devices is passed through or adjacent the wireless encoder. The wireless encoder may be used to pre-program or otherwise configure each wireless communication device for a particular application.
Many existing wireless encoders use radio frequency couplers in the form of transmission lines terminated with matched loads. The fields emerging from such radio frequency couplers are typically not well contained and are strongly affected by the propagation environment inside the wireless encoder and by the form factor of wireless communication devices passing by the coupler. Thus, such wireless encoders may be inefficient in attempting to communicate with wireless communication devices of various shapes and sizes within wireless encoders having different metal parts.
In order to write to each wireless communication device separately, the wireless encoder may use a short-range, less powerful antenna in an attempt to encode only the nearest wireless communication device as it passes.